Hydraulic system

ABSTRACT

A hydraulic system, especially for motor vehicles includes a master cylinder, a slave cylinder and a pressure medium line connected thereto. The invention provides a hydraulic system which is simple or economical to produce by virtue of the fact that the hydraulic system includes at least one hydraulic plug-type connection with a plug connector and a socket contact and the plug connector includes an abutment and a sealing element which are made of different materials and which are connected together in a material fit.

The present invention is directed to a hydraulic system, in particularfor motor vehicles, including a master cylinder, a slave cylinder, adamping device, and a pressure-medium line which connects them.

A hydraulic system of this type is known, for example, from GermanPatent Application DE 101 06 958 A1. Hydraulic systems of this kind areused in motor vehicles, in particular, as devices for actuating brakes,as steering aids, and as devices for actuating friction clutches, forexample in the power flow between an internal combustion engine and atransmission, or between an electrical machine and a drive train.

The inherent disadvantage of related-art hydraulic systems is thesubstantial outlay required for manufacturing.

It is, therefore, an object of the present invention to provide ahydraulic system that is simpler and more cost-effective to manufacture.

This objective is achieved by a hydraulic system as set forth in claim1. The present invention provides for the hydraulic system to have atleast one hydraulic plug-in connection having a plug connector, as wellas a plug socket, and for the plug connector to have an abutment and asealing element, which are made of different materials and areintegrally joined to one another. In this case, the abutment isunderstood to be a part of the plug connector which may be introduced atleast partially into a corresponding plug socket. In this context, theabutment itself does not have any sealing function, but rather, becauseof a substantially positive (i.e., form-locking) connection with theplug socket, is used for transmitting mechanical forces, for examplebuckling forces or the like, between the plug connector and the plugsocket. The actual sealing function is assumed by the sealing element.The abutment and the sealing element are fabricated from differentmaterials, the different materials being integrally joined to oneanother. The plug connector is preferably manufactured from a plastic inan injection molding process, the abutment and the sealing element madeof different materials being manufactured in one or two successiveoperations. This may be accomplished in one and the same injection moldor in different injection molds.

In addition to the integral connection between the abutment and thesealing element, a form-locking connection between the abutment andsealing element may be provided. The form-locking connection may beproduced, for example, by a partial penetration of the differentmaterials in the form of bulges and pockets or by a groove andtongue-type arrangement.

The abutment is preferably fabricated from an injection-moldableplastic, for example an elastomer. The sealing element is preferablyfabricated from a thermoplastic elastomer, a liquid silicon rubber, ageneral purpose elastomer, or a combination of these materials. Withrespect to their elasticity and surface condition, plastics of this kindexhibit optimal material properties for producing an imperviousconnection.

An external bead is preferably integrally molded on the sealing element.In this context, the bead is dimensioned in such a way that its outerperiphery is larger than the inner periphery of the part of the plugsocket corresponding thereto. In this manner, the outer bead of thesealing element exerts a surface pressure on parts of the inner surfaceof the connector element when connection is made with the connectorelement, thereby producing a sealing connection.

In the same way, an inner bead may be integrally molded on the sealingelement. Its purpose is to sealingly connect the plug connector to ahydraulic line fitted into the same. To that end, the inner diameter ofthe inner bead is smaller than the outer diameter of the hydraulic line.Both the inner as well as the outer bead are disposed substantiallyrotationally symmetrically over the entire periphery of the sealingelement.

A further refinement of the hydraulic system provides for the plugconnector to include an annular groove into which a clamping spring mayengage, a non-positive and/or positive connection being able to beproduced between the plug connector and a plug socket via the clampingspring. The clamping spring is typically fastened to the plug socket,for example in a groove or in one or more bores. The connection betweenthe plug connector and the plug socket is established simply by pressingthe plug connector into the plug socket. The connection may be released,for example, by pulling the clamping spring out of the socket.Alternatively, a non-circumferential groove may be provided in place ofan annular groove in the plug connector, so that, by axially twistingthe plug connector, the clamping spring is pressed to the outside,thereby enabling the connection between the plug connector and the plugsocket to be released.

In addition, it may be provided for the abutment and the sealing elementto be fabricated from differently dyed materials. This measure makes itpossible to identify different plug connector designs, for exampledifferent plug connector diameters, different test pressures, ordifferent sealing formations.

The objective mentioned at the outset is also achieved in that thehydraulic system includes at least one hydraulic plug-in connectionhaving a plug connector and a plug socket, in that the plug-inconnection includes an arrangement of a clamping spring and at least onegroove for providing the non-positive and/or positive connection betweenthe plug connector and the plug socket, and in that the clamping springis wavy and/or bent. Therefore, when viewed from the side, the clampingspring is not flat, but rather bent in an angular, semicircular or waveshape. As a result of this refinement, given a manufactured plug-inconnection, the clamping spring rests in the installed position betweenthe plug connector and the plug socket in the groove in such a way thatthe plug connector is axially fixed without play.

The groove is preferably an annular groove. The groove may alternativelybe made up of individual grooves which are placed, for example, onopposite sides of the plug connector. An annular groove is simpler tomanufacture than individually placed grooves.

The height of the annular groove is preferably greater than the heightof the clamping spring, so that the clamping spring rests under axialtension in the groove. This means that if the clamping spring were flatand not bent in accordance with the present invention, it would be fixedin the groove with perceptible play. Because of its wavy or bent form,the clamping spring rests in the installed position under axial tensionin the groove. The clamping spring thereby effects an axial,free-from-play connection between the plug connector and the plugsocket.

An alternative embodiment of the hydraulic system according to thepresent invention provides for the hydraulic system to include at leastone hydraulic plug-in connection having a plug connector and a plugsocket, the plug-in connection including an arrangement of a clampingspring and at least one groove for providing the non-positive and/orpositive connection between the plug connector and the plug socket, anda spring element being positioned between an end face of the plugconnector and a base area of the plug socket. The spring element pressesapart the plug connector and the plug socket in the axial directionagainst the motion of the clamping spring. This enables a connection tobe established that is substantially free from play between the plugsocket and the plug connector.

The spring element is preferably a corrugated washer. A corrugatedwasher is especially simple to manufacture and particularly easy tohandle when producing the connection between the plug connector and theplug socket.

The two initially alternative specific embodiments of the hydraulicplug-in connection may also be combined by designing the clamping springand the groove, as well as the spring element in accordance with thepresent invention.

The objective mentioned at the outset is also achieved by a hydraulicsystem which includes a damping device, the damping device having a hosebarb for connection to the pressure-medium line. The hose barb makes itpossible to connect the damping device directly to the pressure-mediumline. In addition, this measure reduces the space required for thedamping device. The barb is located on the damping device in place ofone of the connectors.

The hose barb is preferably integrally formed in one piece with thedamping device. For example, the hose barb may be integrally formed inone piece with a housing element of the damping device. This measuremakes it possible for the hose barb to be manufactured with the housingelement, for example, in one operation. In this case, for example, awelded connection is suitable as a one-piece connection. Alternatively,the hose barb may be integrally cast in one piece with a housing part ofthe damping device.

In one alternative embodiment of the present invention, the hose barb isdetachably secured to the damping device. For example, the hose barb maybe bolted to the damping device or have a bayonet fitting type ofconnection.

The objective mentioned at the outset is also achieved by a hydraulicsystem having a damping device which includes a switchable orifice.Switchable orifice is understood here to mean that the orifice is onlyeffective in one direction of flow. In this manner, the function of anorifice, which is only effective in one direction and acts as anindependent component part, and the function of the damping device arecombined in one component. As a result, it is not only possible toreduce the outlay for assembly, but for manufacturing costs as well, ascompared to an assemblage of two individual components.

In one preferred embodiment, the damping device includes both a first aswell as a second valve. Another embodiment of the present inventionprovides for the first valve to open in response to the damping devicebeing traversed by flow from the master cylinder side to the slavecylinder side, and for the second valve to open in response to thedamping device being traversed by flow from the slave cylinder side tothe master cylinder side. In this context, the switchable orifice ispreferably positioned in such a way that it is traversed by flow whenthe damping device is traversed by flow from the slave cylinder side tothe master cylinder side. The switchable orifice is preferably situatedbehind the second valve when the damping device is traversed by flowfrom the slave cylinder side to the master cylinder side.

One preferred embodiment of the hydraulic system according to thepresent invention provides for the valves to be constituted of passageopenings and of at least one hose sleeve, the hose sleeve being able toseal the passage openings in one direction of flow in each case and openthem in the other direction of flow. Such an embodiment of the valvesrenders possible an especially reliable blocking effect and,respectively, hydraulic conductivity in the context of an especiallysimple assembly and manufacture of individual parts.

The damping device preferably includes both a first as well as a secondhousing part, the second housing part having a valve section including afirst channel and a second channel. In this manner, the essentialfunctional elements of the damping device are integrated in the secondhousing part, so that only the second housing part is expensive tomanufacture, and the first housing part is a comparatively simplehousing component.

In one embodiment of the damping device, the hose sleeve includes asealing bead for sealing off the first housing part from the secondhousing part. This measure eliminates the need for other sealing means,such as a special seal, between the housing parts, thereby simplifyingthe assembly of the damping device.

The objective mentioned at the outset is also achieved by a hydraulicsystem in which a pressure-line connection is provided having means forventing the hydraulic actuating system, and in which the pressure-lineconnection has an axially rotatable sleeve having a first vent bore,which, together with at least one second vent bore, forms a sealablevalve. The hydraulic actuating system is able to be vented by way of thesealable valve. In general, there is no need for any further valves inthe hydraulic actuating system. In addition, the valve mounted directlyon the pressure-line connection is easily accessible in the installedstate.

Another embodiment provides for a second vent bore to be introduced intoa hollow tubular connecting member and for a hose gasket having a thirdvent bore to be situated on the tubular connecting member, the secondand third vent bore being positioned more or less axially with respectto one another, and a rotatable sleeve having a first vent bore beingsituated on the hose gasket, the first vent bore being disposed in afirst position of the rotatable sleeve more or less axially with respectto the second vent bore and, in a second position, outside of an overlapregion of the second vent bore. Both the hose gasket as well as thesleeve formed as a plastic ring are commercial components. The vent maybe opened or closed by a 180° rotation of the sleeve about thelongitudinal axis, which is ensured by an anti-rotation element having alimit stop. Potential leakage is prevented by placing a bead around thevent bore on the adapter plug connector. Any twisting of the hose gasketis prevented by the placement of the tubular connecting member andgroove in the respective parts. Any possible twisting and/or slipping ofthe plastic ring is achieved by providing a latching function on theadapter plug connector and simultaneous clamp locking using wire formsprings.

The sleeve is preferably transferred by axial rotation from the firstposition into the second position. Instead of an axial rotation, anaxial displacement of the sleeve would also be possible in this case.

The sleeve is preferably fixed to the tubular connecting member in theaxial direction by a stop spring. In spite of an axially fixedarrangement, a connection of this kind still permits a rotation aboutthe axial axis.

The sleeve preferably locks into place in the closed rotationalposition. Here, ‘locking into place’ is understood to mean that aninitial resistance must first be overcome in order to rotate the sleeve.This measure prevents the vent valve from being unintentionally openedand, at the same time, it indicates, by the locking function, when theclosed position has been reached. In addition, this measure prevents anunintentional opening during operation, for example due to vibrations orthe like.

The objective mentioned at the outset is also achieved by a hydraulicsystem in which provision is made for a pressure-line connection and forat least parts of the pressure-line connection to be produced using agas- or fluid-injection method. This measure also makes it possible forbent or rounded molded parts to be produced.

Another embodiment of the pressure-line connection according to thepresent invention includes at least one plug connector and/or one socketwhose hollow space is produced using a mold core. This makes it possibleto improve the molding accuracy and the surface condition of the plugconnectors and, respectively, of the plug sockets.

Exemplary embodiments of the present invention are described in greaterdetail below with reference to the accompanying drawings. Specifically,the figures show:

FIG. 1: a schematic representation of a hydraulic system on the basis ofan exemplary embodiment of a clutch release device;

FIG. 2: a diagrammatic sketch of a hydraulic plug-in connection inlongitudinal section;

FIG. 3: a longitudinal section through a first specific embodiment of aplug connector according to the present invention;

FIG. 4: a longitudinal section through a second specific embodiment of aplug connector according to the present invention;

FIG. 5: a longitudinal section through a third specific embodiment of aplug connector according to the present invention;

FIG. 6: a part sectional view of a first fastening arrangement of ahydraulic plug-in connection;

FIG. 7: a clamping spring for use in an arrangement in accordance withFIG. 6;

FIG. 8: a second fastening arrangement of a hydraulic plug-inconnection;

FIG. 9: a damping device in accordance with the present invention in apart sectional view;

FIG. 10: a damping device having an integrated, switchable orifice;

FIG. 11: an exploded view of a pressure-line connection in accordancewith the present invention;

FIG. 12: a pressure connection in accordance with the present invention,in a plan view according to FIG. 11;

FIG. 13: a section along A-A in FIG. 12 in a first position;

FIG. 14: a section along A-A in FIG. 12 in a second position;

FIG. 15: a section through a first specific embodiment of apressure-line connection according to the present invention;

FIG. 16: a part sectional view of a second specific embodiment of apressure-line connection according to the present invention.

FIG. 1 schematically shows one possible embodiment of a hydraulic systemhaving a pressure-limiting valve 90, considering as an example a clutchrelease device 91 having a master cylinder 92 and a slave cylinder 93.In the exemplary embodiment shown, pressure-limiting valve 90 isinstalled in line sections 99 and 100 and separates them from oneanother in the unopened state. It is understood that in other exemplaryembodiments, pressure-limiting valve 90 may be integrated in mastercylinder 92 or in slave cylinder 93, and in other hydraulic systems,such as brake systems, power steering systems, and the like, it may beintegrated in a functional component. In addition, a pressure-limitingvalve according to the present invention may be advantageously used inany hydraulic line system as a pressure-limiting valve and/or as anoscillation filter, for example as a so-called “pulsation filter”.

Clutch release system 91 hydraulically operates clutch 95 by acting uponmaster cylinder 92 via an actuating member 102, which may be a footpedal, an actuator, such as an electrical actuator, or the like. In thismanner, a mechanical transmission means 101 builds up pressure in mastercylinder 92, which, via line section 100, pressure-limiting valve 90,and line section 99, builds up pressure in slave cylinder 93. As shownin this example, slave cylinder 93 may be arranged concentrically aroundtransmission input shaft 98 and be axially supported on a transmissionhousing (not shown), and, via a release bearing, may impart thenecessary release force to clutch 95, respectively, to its releaseelements, such as the disk springs. Further embodiments may provide fora slave cylinder 93, which actuates a disengagement element via adisengagement mechanism, and which is located outside of the clutchbell; the slave cylinder axially loading the disengagement mechanism viaa piston which is in hydraulic communication with the master cylinderand accommodated in the slave cylinder housing. To apply the releaseforce, the slave cylinder is immovably secured to the transmissionhousing (not specifically shown here), or to another component that isimmovably fixed to the housing. When clutch 95 is closed, transmissioninput shaft 98 transmits the torque of internal combustion engine 96 toa transmission (not specifically shown), and then to the drive wheels ofa motor vehicle.

Crankshaft 97 is subjected to irregular loading as a result of thecombustion processes in internal combustion engine 25 and as a functionof the design of internal combustion engine 96, depending, for example,on the number of cylinders. The irregular loads are manifested in thecrankshaft as axial and/or wobbling vibrations and are transmittedthrough disengagement mechanism 94 to slave cylinder 93, line system 99,100, to master cylinder 92, and, from there, via mechanical connection101 to actuating member 102. If the actuating member is a clutch pedal,these vibrations are perceived as an annoyance. In the case thatactuating member 102 is an actuator, such vibrations can result, forexample, in reduced control accuracy, or in a shortened service life.Pressure-limiting valve 90 is therefore inserted in lines 99, 100 fordamping purposes, and tuned to damp the vibrations introduced bycrankshaft 97. Such vibrations typically fall in the frequency range of50 to 200 Hz.

FIG. 2 shows a longitudinal section through a hydraulic plug-inconnection 1, which includes a plug connector 2, as well as a plugsocket 3. In this context, the purpose of FIG. 2 is first to clarify theuse and interaction of the plug connector and plug socket. Both plugconnector 2, as well as plug socket 3 are connected to pressure-mediumlines 99, 100 (not shown in FIG. 2), in accordance with FIG. 1. Plugconnector 2 has a circumferential annular groove 4, into which aclamping spring 6 introduced into a recess 5 engages in the installedstate.

FIG. 3 shows a longitudinal section of a first specific embodiment of aplug connector 2 according to the present invention. It is composed ofan abutment 7, as well as of a sealing element 8 positioned on the endface of abutment 7. Both abutment 7, as well as sealing element 8 aremade of a plastic, however each of a different plastic. Depending on thedesired field of application, abutment 7 may be made of any desiredplastic of sufficient strength, preferably of a thermoplastic plastic,so that the component may be manufactured by injection molding orsimilar methods. The sealing element is preferably made of athermoplastic elastomer (TPE), liquid silicon rubber (LSR), or of anyother elastomer.

Plug connector 2 is preferably manufactured in an injection moldingprocess, abutment 7 and sealing element 8 made of a different materialbeing manufactured in one or two successive operations. This may beaccomplished in one and the same injection mold or in differentinjection molds. Thus, two different plastics are introduced into theinjection mold simultaneously or successively, the different plasticsbeing introduced in such a way that abutment 7 is fabricated from oneplastic, sealing element 8 from the other plastic. Abutment 7 andsealing element 8 are integrally joined to one another at their point ofcontact.

FIG. 4 depicts another specific embodiment of a plug connector 2according to the present invention, in which the connection betweenabutment 7 and sealing element 8 is designed to be integral as wellform-locking. To that end, integrally molded on the end face of abutment7 is an annular extension 9, upon which is placed a sealing element 8having a bead 10 corresponding thereto. In this case, sealing element 8,as well as abutment 7 may be fabricated as separate plastic parts andfirst be joined together afterwards, for example via a bonded adhesiveconnection or latching-type snap-on connections. In the same way, inaccordance with the specific embodiment of FIG. 4 and similarly to thatof FIG. 3, plug connector 2 may be fabricated from different plastics inone or more operations. For example, abutment 7 may initially befabricated in one injection mold and, in another injection mold, its endface may be provided with sealing element 8 made of another plastic.

Sealing element 8 is provided with an outer circumferential bead 10which seals off plug connector 2 from plug socket 3. In addition, aninner bead 11 may be situated on the inside of sealing element 8. Itspurpose is to seal off plug connector 2 from a hydraulic tubing 12 of apressure-medium line 99 and, respectively, 100 in accordance with FIG.1, which is inserted into plug connector 2. To facilitate assembly, achamfer 13, as shown in FIG. 3, may be configured on the end face ofsealing element 8 facing plug socket 3.

FIG. 5 shows a modified embodiment of the plug-in connection inaccordance with FIG. 4. Here, both annular extension 9, as well ascorresponding sealing element 8 are provided with a circumferentialchamfer 13 to facilitate assembly.

The color of the plastic of sealing element 8 may differ from that ofthe plastic of abutment 7. The different colors may be used, forexample, as a basis for identifying plug connector 2.

The abutment is preferably manufactured in an injection molding process,in which abutment 7 has different physical and chemical properties thansealing element 8. To that end, in the present exemplary embodiment,different plastics are selected for abutment 7 and for sealing element8.

FIG. 6 shows a diagrammatic sketch of a hydraulic plug-in connection ina part sectional view. The fastening arrangement corresponds alonggeneral lines to the representation of FIG. 2. Therefore, identicalcomponents have the same designations. A plug connector 2 is detachablyconnected to a plug socket 3. To that end, a clamping spring 6 engagesin an annular groove 4 of plug connector 2. Alternatively, the annulargroove may be designed as a groove-like notch or in the form of twomutually opposing, individual grooves. Clamping spring 6 may be placedvia a recess 5 in plug socket 3, along the lines of the representationof FIG. 2, or be placed in plug socket 3 via a through hole (not shownin greater detail). Plug connector 2 is inserted axially into plugsocket 3 during manufacture of the hydraulic plug-in connection. Due tothe substantially conical outer form of plug connector 2, clampingspring 6 is pressed to the outside and is able to snap into annulargroove 4, as soon as plug connector 2 is introduced far enough into plugsocket 3. A positive and/or non-positive connection of plug connector 2with plug socket 3 is formed in this manner. An O-ring 14 is positionedin an O-ring groove 15 of plug connector 2 and, in the installed statedepicted in FIG. 6, rests against the inner wall of plug socket 3, inwhich the plug-in connection is sealingly established. Height D4 ofannular groove 4 is greater than height D6 of clamping spring 6.Clamping spring 6 shown in a side view in FIG. 7 is angled.

FIG. 8 shows an alternative embodiment of the plug-in connectionaccording to the present invention. Here, an ondular washer 18 ispositioned between an end face 16 of plug connector 2 and a base area 17of plug socket 3. In this context, FIG. 8 shows the sealingly producedhydraulic plug-in connection 1 between plug connector 2 and plug socket3. When producing the connection, plug connector 2 is to be pressedagainst a spring force produced by ondular washer 18 into plug socket 3to the point where clamping spring 6 snaps into place in annular groove4.

FIG. 9 shows a damping device 20, a so-called pulsation filter, whichmay be placed in hydraulic systems for damping unwanted pressurefluctuations in a hydraulic line. Damping device 20 is provided with aplug-in connection 21 for connection to a clutch (not shown), forexample to a central release mechanism of a motor vehicle clutch. Thefunction of the generally known damping device 20 will not be discussedin greater detail here. A hose barb connection 22 is flange-mounted onthe side of damping device 20 opposing plug-in connection 21. A hose 23may be secured with the aid of hose fitting 24 to hose barb 22. Hosefitting 24 is provided in a generally known manner with a press-fitlocation 26, making it possible for a frictionally locked connection tobe established between hose barb 22 and hose 23. Hose barb 22 isintegrally formed in one piece with damping device 20, for example byforming a welded connection, or by manufacturing the housing of thedamping device and hose barb 22 in one piece, for example by casting,lathing, forging, or the like. Alternatively, hose barb 22 may bedetachably connected to damping device 20, for example by a screwconnection.

FIG. 10 shows a damping device 20, also referred to as a pulsationfilter, which may also be inserted as an additional component into apressure-medium line 99, 100 (not shown in greater detail). To that end,it is provided with a plug connector 31, as well as with a plug socket32. Plug connector 31 may be designed both in accordance with therelated art as well as in accordance with one of the embodimentspreviously described with reference to FIGS. 2 through 7. Plug socket 32may be designed in accordance with plug socket 3 previously clarifiedwith reference to FIGS. 2 through 7 or, however, be replaced by a hosebarb 22 in accordance with the embodiment described with reference toFIG. 9. Plug connector 31 is connected to a slave cylinder 93 (not shownhere). Correspondingly, plug socket 32 is connected to a master cylinder92 (not shown here).

Damping device 20 includes a first housing part 33, as well as a secondhousing part 34. The two housing parts 33, 34 are sealed off from oneanother in a pressure-tight manner by a gasket ring 35. The secondhousing part 34 includes a valve section 36 situated within firsthousing part 33. This valve section 36 includes a first channel 37 whichleads via a first passage opening 38 into an annular space 39 betweenfirst housing part 33 and second housing part 34. A second channel 40 iscomposed of a first region 40 a, as well as of a second region 40 b.Second region 40 b extends substantially radially in the circumferentialdirection between first and second housing part 33, 34 and forms anannular space there. First and second regions 40 a, 40 b are joined toone another by a second passage opening 41. An orifice 42 establishes aconnection between the second region of second channel 40 b and firstchannel 37. Valve section 36 is surrounded by a hose sleeve 43, which,with first passage opening 38 and second passage opening 41, in eachcase forms a valve that is permeable in only one direction. Hose sleeve43 includes a circumferential sealing bead 44 which seals off the secondregion of second channel 40 b from annular space 39.

Together with hose sleeve 43, first passage opening 38 forms a firstvalve 45. Correspondingly, together with hose sleeve 43, second passageopening 41 forms a second valve 46.

When damping device 20 is traversed by flow from the master cylinderside to the slave cylinder side, as illustrated in FIG. 10 by an arrow47, this takes place in the direction of flow of first valve 45. In thiscase, a flow is possible through first channel 37 and through firstvalve 45 into annular space 39. In the opposite direction, as indicatedby an arrow 48 in FIG. 10, the direction of flow is from slave cylinder93 to master cylinder 92 via annular space 39, the first region ofsecond channel 40 a and second valve 46 into the second region of secondchannel 40 b. The hydraulic fluid may then continue to flow acrossorifice 42 into first channel 37. Thus, orifice 42 makes it possible foran additional resistance to flow that is only effective in one directionof flow to be incorporated into damping device 20.

A plurality of first passage openings 38, as well as a plurality ofsecond passage openings 41 may also be distributed over the periphery ofdamping device 20, so that a plurality of valves may be formed here. Asthrottle channels, the passage openings are adapted in diameter and formto the throttling conditions, i.e., the damping requirements. Hosesleeve 43 is fabricated from an elastic plastic or rubber material. Hosesleeve 43 may, in sections, be reinforced or have a multilayerconstruction. It may be reinforced, for example, by fabric, or by ringsor spirals of plastic or metal. Hose section 43 is preferably fittedonto valve section 36 under pretensioning action.

FIG. 11 shows an exploded view; FIGS. 12 and 13 a plan view and sideview, respectively, of a pressure-line connection 50 according to thepresent invention. Pressure-line connection 50 includes a first plugconnector 51, as well as a second plug connector 52. Here, pressure-lineconnection 50 is designed to have an approximately 90° angle. However,other angles or a rectilinear design are also conceivable. Pressureconnection 50 has an altogether hollow design and forms an interiorspace 68 through which hydraulic fluid or the like may flow. A hose seal54 having a vent bore 55 is slid over a tubular connecting member 53.Hose seal 54 is provided with a groove-type cutout 56 which is able toengage with tongue-type projection 57 and, in the installed state,prevents hose seal 54 from rotating in relation to tubular connectingmember 53. A sleeve 58, which is rotationally mounted on hose seal 54and, respectively, on tubular connecting member 53 is slid over hoseseal 54.

Sleeve 58 is axially fixed to tubular connecting member 53 by a stopspring 59, which is insertable into a recess 60 of sleeve 58 and, in theinstalled state, engages in an annular groove 61 of tubular connectingmember 53. In spite of being axially fixed to this tubular connectingmember 53, in the installed state, sleeve 58 is positioned in a way thatpermits radial rotation. A hose connection 62, which is provided with aclosure cap 63 a, is arranged on sleeve 58. Hose connection 62 includesa vent bore 67, which, in one rotational position of sleeve 58, isbrought into coincidence with vent bore 55 of hose seal 54. A vent bore64, which, in the installed state of hose seal 54, is in alignment withvent bore 55 of hose seal 54, is introduced into tubular connectingmember 53.

Indentations which, in specific rotational positions, effect a latchingfunction with sleeve 58 and thus with stop spring 59, are introducedinto annular groove 61, so that, in this rotational position, anincreased initial torque force must be overcome to rotate sleeve 58. Inthis manner, the sleeve is arrested in this position. Preferably, thisposition is selected in such a way that the bore of hose connection 62is not in alignment and thus not coincident with vent bore 55.

A bracket 65, which may be used to attach pressure-line connection 50 tothe clutch bell of a motor vehicle (not shown), is configured onpressure line connection 50. In the installed state of pressure-lineconnection 50, a web 66 is used to sealingly cover an opening introducedinto the clutch bell (not shown here) for feeding through pressure-lineconnection 50.

The function of the pressure-line connection in accordance with thepresent invention is illustrated in FIGS. 13 and 14. FIG. 13 shows asection along A-A in FIG. 12. Here, a closed position of thepressure-line connection is shown. In this case, vent bore 67 of hoseconnection 62 is axially rotated 180° relatively to vent bore 55 of hoseseal 54 and, respectively, to vent bore 64 of tubular connecting member53. Therefore, no hydraulic fluid is able to leak from interior space 68through vent bore 67.

A second vent bore 64 is introduced into hollow tubular connectingmember 53. A hose seal 54 having a third vent bore 55 is situated ontubular connecting member 53, second vent bore 64 and third vent bore 55being positioned more or less axially with respect to one another, and arotatable sleeve having a first vent bore 67 being situated on hose seal54, first vent bore 67 being disposed in a first position of rotatablesleeve 58 more or less axially with respect to second vent bore 64 and,in a second position, outside of an overlap region of second vent bore64.

In a second representation in accordance with FIG. 14, sleeve 58 andthus also vent bore 67 of hose connection 62 are rotated 180° relativelyto the representation of FIG. 13, so that this is coincident with ventbores 55 of hose seal 54 and, respectively, with vent bore 64 of tubularconnecting member 53 and allows gas or hydraulic fluid to escape frominterior space 68. Therefore, in this rotational position of sleeve 58,a venting of the entire hydraulic system is possible.

FIG. 15 depicts a pressure-line connection 70 which is provided with aplug connector 71, as well as with two plug sockets 72. Thepressure-line connection is used for connecting a hydraulic line (notshown in greater detail), for example, to a hydraulic central-releasesystem of a motor vehicle. Pressure-line connection 70 is hollow overits entire length. This is characterized as hollow space 73 in FIG. 15.In the installed state, the pressure-line connection is traversed by theflow of a fluid, for example a hydraulic fluid. In the same manner asother housing parts, the pressure-line connections often contain longand thin hollow regions. Typically, components of this kind arefabricated using plastic injection molding processes. In accordance withthe related art, cores are used inside the injection mold to producehollow spaces. For long and thin hollow spaces, correspondingly long andthin cores are to be used which exhibit little mechanical stability andhave the inherent risk of deformation. In addition, when working withcores of this kind, the heat dissipation is problematic. To permitdemolding, the cores are designed with a straight bore axis. When coresof this kind are used, the design possibilities of the pressure-lineconnection are limited.

As can be directly inferred from FIG. 15, pressure-line connection 70 isa comparatively long and thin component having an elongated hollow space73. Typically, when manufactured out of plastic, a very long and thincore is to be placed in an injection mold or the like. In themanufacturing method according to the present invention, instead ofintroducing a long, thin core into hollow space 73 during fabrication,the hollow space is produced directly by injecting a gas or a liquid.When the gas or fluid injection method is used, a balloon-like plasticfilm is molded by one or more injection molding nozzles into a negativemold of pressure-line connection 70. The balloon-like plastic filmpositions itself against the inside of the negative mold and fills inthe bulges as exemplified by a circumferential fastening web 74 in thecase of the present pressure-line connection 70. The inner surface has asubstantially even, although relatively rough quality. It is designatedas free surface 75 in FIG. 15. Regions in which complicated surfaceforms are required, such as the region of plug connector 71 or that ofplug sockets 72, are produced using mold cores 76, 77. Shown hereexemplarily are only one first mold core 76 for manufacturing plugsockets 72, as well as one second mold core 77 for manufacturing plugconnector 71.

By using the manufacturing method described in principle with referenceto FIG. 15, it is also possible to produce more complicated hollowspaces as one-piece injection-molded components. For example, FIG. 16shows a distinctly curved pressure-line connection 80, which has acurvature 81 of greater than 90°. In this context, a first substantiallystraight region 82 and a second substantially straight region 83 arejoined by curvature 81. For that purpose, existing manufacturing methodsrequired that a hole remain in the extension of section region 83, inthe area of an outer curvature 84, in order to introduce a mold core.This hole was then closed by a plug, which was welded or bonded, forexample. By using the manufacturing method described here, the need iseliminated for introducing a plug of this kind as an additionaloperation.

The claims filed with the application are proposed formulations and donot prejudice the attainment of further patent protection. The applicantreserves the right to claim still other combinations of features that,so far, have only been disclosed in the specification and/or thedrawings.

The antecedents used in the dependent claims refer, by the features ofthe respective dependent claim, to a further embodiment of the subjectmatter of the main claim; they are not to be understood as renouncingattainment of an independent protection of subject matter for thecombinations of features of the dependent claims having the main claimas antecedent reference.

Since, in view of the related art on the priority date, the subjectmatters of the dependent claims may form separate and independentinventions, the applicant reserves the right to make them the subjectmatter of independent claims or of divisional applications. In addition,they may also include independent inventions, whose creation isindependent of the subject matters of the preceding dependent claims.

The exemplary embodiments are not to be understood as limiting the scopeof the invention. Rather, within the framework of the presentdisclosure, numerous revisions and modifications are possible, inparticular such variants, elements and combinations and/or materials,which, for example, by combining or altering individual features orelements or method steps described in connection with the generaldescription and specific embodiments, as well as the claims, andcontained in the drawings, may be inferred by one skilled in the artwith regard to achieving the objective, and lead, through combinablefeatures, to a new subject matter or to new method steps or sequences ofmethod steps, also to the extent that they relate to manufacturing,testing, and operating methods.

1-37. (canceled)
 38. A hydraulic system comprising: a master cylinder; aslave cylinder; a pressure-medium line connecting the master cylinder tothe slave cylinder; and at least one hydraulic plug-in connection havinga plug connector and a plug socket, the plug connector including anabutment made of a first material and a sealing element made of a secondmaterial, the abutment integrally joined with the sealing element. 39.The hydraulic system as recited in claim 38, wherein the hydraulicsystem is part of a motor vehicle.
 40. The hydraulic system as recitedin claim 38, wherein the abutment and the sealing element are integrallyjoined to one another in a form-locking manner.
 41. The hydraulic systemas recited in claim 38, wherein the abutment includes at least one of aninjection moldable plastic, a thermoplastic elastomer, a liquid siliconrubber, and a general purpose elastomer.
 42. The hydraulic system asrecited in claim 38, wherein the plug connector includes one of anexternal bead and an inner bead integrally molded on the sealingelement.
 43. The hydraulic system as recited in claim 38, wherein theplug connector includes has an annular groove and further comprising aclamping spring engaged in the annular groove, wherein the plugconnector and the plug socket are connectable.
 44. The hydraulic systemas recited in claim 43, wherein the plug connector and the plug socketare connectable in a positive locking manner.
 45. The hydraulic systemas recited in claim 38, wherein the first material has a first color andthe second material has a second color.
 46. A hydraulic systemcomprising: a master cylinder; a slave cylinder; a damping device; apressure-medium line connecting the master cylinder, the slave cylinderand the damping device; and at least one hydraulic plug-in connectionincluding a plug connector, a plug socket, and a connecting arrangementconfigured to provide a connection between the plug connector and theplug socket, wherein the connecting arrangement includes a bent clampingspring and at least one groove.
 47. The hydraulic system as recited inclaim 46, wherein the bent clamping spring is wavy.
 48. The hydraulicsystem as recited in claim 46, wherein the connecting arrangement isconfigurd to provide a non-positive connection between the plugconnector and the plug socket.
 49. The hydraulic system as recited inclaim 46, wherein the at least one groove is an annular groove having aheight greater than a height of the clamping spring and wherein theclamping spring is disposed under axial tension in the groove.
 50. Ahydraulic system comprising: a master cylinder; a slave cylinder; adamping device; a pressure-medium line connecting the master cylinder,the slave cylinder and the damping device; at least one hydraulicplug-in connection having a plug socket defining a base area, a plugconnector having an end face, and a connection arrangement configured toprovide a connection between the plug connector and the plug socket,wherein the connecting arrangement includes a clamping spring and atleast one groove; and a spring element disposed between the end face ofthe plug connector and the base area of the plug socket.
 51. Thehydraulic system as recited in claim 50, wherein the spring elementincludes a corrugated washer.
 52. A hydraulic system comprising: amaster cylinder; a slave cylinder; a damping device; and apressure-medium line connecting the master cylinder, the slave cylinderand the damping device, wherein the damping device has a hose barb forconnection to the pressure-medium line.
 53. The hydraulic system asrecited in claim 52, wherein the hose barb is integrally joined in onepiece to the damping device.
 54. The hydraulic system as recited inclaim 53, wherein the hose barb is detachably integrally joined in onepiece to the damping device.
 55. A hydraulic system comprising: a mastercylinder; a slave cylinder; a damping device including a switchableorifice; and a pressure-medium line connecting the master cylinder, theslave cylinder and the damping device.
 56. The hydraulic system asrecited in claim 55, wherein the damping device includes a first valveand a second valve.
 57. The hydraulic system as recited in claim 56,wherein the first valve is configured to open in response to the dampingdevice being traversed by a flow from the master cylinder to the slavecylinder, wherein the second valve is configured to open in response tothe damping device being traversed by a flow from the slave cylinder tothe master cylinder, and wherein the switchable orifice is disposedbehind the second valve and is likewise traversed by the flow from theslave cylinder to the master cylinder.
 58. The hydraulic system asrecited in claim 56, wherein the first valve includes a first passageopening and the second valve includes a second passage opening, andwherein a hose sleeve is configured to seal the first passage openingand to open the second passage opening in a first flow direction and toopen the first passage opening and to seal the second passage open in asecond flow direction.
 59. The hydraulic system as recited in claim 58,wherein the damping device includes a first housing part and a secondhousing part having a valve section with a first channel and a secondchannel, the second channel including first and second subsections. 60.The hydraulic system as recited in claim 59, wherein the hose sleeveincludes a sealing bead configured to seal off the first housing partfrom the second housing part.
 61. A hydraulic system comprising: amaster cylinder; a slave cylinder; a damping device; a pressure-mediumline connecting the master cylinder, the slave cylinder and the dampingdevice; and a pressure-line connection arrangement configured to ventthe hydraulic system and including a second vent bore and an axiallyrotatable sleeve having a first vent bore, the second vent bore and theaxially rotatable sleeve forming a sealable valve.
 62. The hydraulicsystem as recited in claim 61, further comprising a hollow tubularconnecting member and a hose gasket having a third vent bore disposed onthe connecting member, the second vent bore and the third vent borebeing positioned substantially axially with respect to one another,wherein the rotatable sleeve is disposed on the hose gasket and moveablebetween a first position in which the first vent bore is disposedsubstantially axially with respect to the second vent bore and a secondposition in which the first vent bore is disposed so as not to overlapwith the second vent bore.
 63. The hydraulic system as recited in claim62, wherein the rotatable sleeve is moved by at least one of an axialrotation and an axial displacement from the first position into thesecond position.
 64. The hydraulic system as recited in claim 61,further comprising a stop spring configured to fixed the sleeve to thetubular connecting member in an axial direction.
 65. The hydraulicsystem as recited in claim 61, wherein the rotatable sleeve isconfigured to lock into place in a closed rotational position of thesleeve.
 66. A hydraulic system comprising: a master cylinder; a slavecylinder; a damping device; a pressure-medium line connecting the mastercylinder, the slave cylinder and the damping device; and a pressure-lineconnection including a portion formed using at least one a gas-injectionand a fluid-injection.
 67. The hydraulic system as recited in claim 66,further comprising at least one of a plug connector and a plug socket,wherein the plug connector or plug socket includes a hollow space. 68.The hydraulic system as recited in claim 66, wherein the hollow space isproduced using a mold core.